The hydrolytic enzyme neuraminidase and its hydrolysis product, N- acetyl neuraminic acid, have been implicated in many aspects of the fertility picture, ranging from involvement in the hormonal control of the female menstrual cycle to an apparent role in the penetration of the ovum by sperm. Thus, they seemingly play a major role in the normal process of reproduction. Surprisingly, little or no effort has been made thus far to exploit this role as a means of fertility control. We propose to prepare a number of analogs of N-acetyl neuraminic acid that should be capable of behaving as inhibitors of the enzyme or antagonizing N-acetyl neuraminic acid itself and, in so doing, interrupt the reproductive process. In addition, analogs of compounds that have shown activity as antagonists of neuraminidase will be prepared. These compounds will be evaluated in tests designed to detect activity against sperm as well as antifertility in the female.